Mortgage Servicing Rights - Valuation Assumptions (Details) - Mortgage servicing rights	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Servicing Assets at Fair Value [Line Items]
Constant prepayment rate	9.00%	11.58%
Discount rate	9.45%	9.25%

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746

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- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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